使用 include 机制，如果 include 参数返回时数组的话，如何去掉 data 层？

使用 include 机制，如果 include 参数返回时单个 item 的时候是可以使用 ArraySerializer 减少 data 层，但是如果参数返回 collection 的话，如何去掉 data 层？
路由：

//获取单个拼音和字列表
        $api->get('pinyins/{pinyin}','PinyinsController@show')->name('api.pinyins.show');

控制器：

public function show(Pinyin $pinyin)
    {
        return $this->response->item($pinyin,new PinyinTransformer());
    }

transformer：

public function includeZitis(Pinyin $pinyin)
    {
        return $this->collection($pinyin->zitis,new ZitiTransformer());
    }

请求：

http://hanzi.test/api/pinyins/1?include=zitis

返回数据：

{
    "id": 1,
    "name": "a",
    "zimu_id": 1,
    "zitis": {
        "data": [
            {
                "id": 1,
                "zi": "阿",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 2,
                "zi": "啊",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 3,
                "zi": "腌",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 4,
                "zi": "吖",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 5,
                "zi": "锕",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 6,
                "zi": "錒",
                "duyin": "ā",
                "img": ""
            },
            {
                "id": 7,
                "zi": "B",
                "duyin": "ā",
                "img": "https://ii.911cha.com/zidian/song48/154/25969.png"
            },
            {
                "id": 8,
                "zi": "B",
                "duyin": "ā",
                "img": "https://ii.911cha.com/zidian/song48/135/20f1e.png"
            },
            {
                "id": 9,
                "zi": "B",
                "duyin": "ā",
                "img": "https://ii.911cha.com/zidian/song48/165/2825a.png"
            },
            {
                "id": 10,
                "zi": "嗄",
                "duyin": "á",
                "img": ""
            },
            {
                "id": 11,
                "zi": "呵",
                "duyin": "a",
                "img": ""
            }
        ]
    }
}